[RFC PATCH 4/4] spapr: Add KVM-on-TCG migration support

[Fabiano Rosas <farosas@linux.ibm.com>]

This adds migration support for TCG pseries machines running a KVM-HV
guest.

The state that needs to be migrated is:

- the nested PTCR value;
- the in_nested flag;
- the nested_tb_offset.
- the saved host CPUPPCState structure;

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>

---
(this migrates just fine with L2 running stress and 1 VCPU in L1. With
32 VCPUs in L1 there's crashes which I still don't understand. They might
be related to L1 migration being flaky right now)
---
 hw/ppc/spapr.c          | 19 +++++++++++
 hw/ppc/spapr_cpu_core.c | 76 +++++++++++++++++++++++++++++++++++++++++
 target/ppc/machine.c    | 44 ++++++++++++++++++++++++
 3 files changed, 139 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f0b75b22bb..6e87c515db 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1934,6 +1934,13 @@ static bool spapr_patb_entry_needed(void *opaque)
     return !!spapr->patb_entry;
 }
 
+static bool spapr_nested_ptcr_needed(void *opaque)
+{
+    SpaprMachineState *spapr = opaque;
+
+    return !!spapr->nested_ptcr;
+}
+
 static const VMStateDescription vmstate_spapr_patb_entry = {
     .name = "spapr_patb_entry",
     .version_id = 1,
@@ -1945,6 +1952,17 @@ static const VMStateDescription vmstate_spapr_patb_entry = {
     },
 };
 
+static const VMStateDescription vmstate_spapr_nested_ptcr = {
+    .name = "spapr_nested_ptcr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = spapr_nested_ptcr_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(nested_ptcr, SpaprMachineState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
 static bool spapr_irq_map_needed(void *opaque)
 {
     SpaprMachineState *spapr = opaque;
@@ -2069,6 +2087,7 @@ static const VMStateDescription vmstate_spapr = {
         &vmstate_spapr_cap_fwnmi,
         &vmstate_spapr_fwnmi,
         &vmstate_spapr_cap_rpt_invalidate,
+        &vmstate_spapr_nested_ptcr,
         NULL
     }
 };
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index efda7730f1..3ec13c0660 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -25,6 +25,7 @@
 #include "sysemu/reset.h"
 #include "sysemu/hw_accel.h"
 #include "qemu/error-report.h"
+#include "migration/cpu.h"
 
 static void spapr_reset_vcpu(PowerPCCPU *cpu)
 {
@@ -174,6 +175,80 @@ static const VMStateDescription vmstate_spapr_cpu_vpa = {
     }
 };
 
+static bool nested_needed(void *opaque)
+{
+    SpaprCpuState *spapr_cpu = opaque;
+
+    return spapr_cpu->in_nested;
+}
+
+static int nested_state_pre_save(void *opaque)
+{
+    CPUPPCState *env = opaque;
+
+    env->spr[SPR_LR] = env->lr;
+    env->spr[SPR_CTR] = env->ctr;
+    env->spr[SPR_XER] = cpu_read_xer(env);
+    env->spr[SPR_CFAR] = env->cfar;
+
+    return 0;
+}
+
+static int nested_state_post_load(void *opaque, int version_id)
+{
+    CPUPPCState *env = opaque;
+
+    env->lr = env->spr[SPR_LR];
+    env->ctr = env->spr[SPR_CTR];
+    cpu_write_xer(env, env->spr[SPR_XER]);
+    env->cfar = env->spr[SPR_CFAR];
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_nested_host_state = {
+    .name = "spapr_nested_host_state",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .pre_save = nested_state_pre_save,
+    .post_load = nested_state_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINTTL_ARRAY(gpr, CPUPPCState, 32),
+        VMSTATE_UINTTL_ARRAY(spr, CPUPPCState, 1024),
+        VMSTATE_UINT32_ARRAY(crf, CPUPPCState, 8),
+        VMSTATE_UINTTL(nip, CPUPPCState),
+        VMSTATE_UINTTL(msr, CPUPPCState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static int nested_cpu_pre_load(void *opaque)
+{
+    SpaprCpuState *spapr_cpu = opaque;
+
+    spapr_cpu->nested_host_state = g_try_malloc(sizeof(CPUPPCState));
+    if (!spapr_cpu->nested_host_state) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_spapr_cpu_nested = {
+    .name = "spapr_cpu/nested",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = nested_needed,
+    .pre_load = nested_cpu_pre_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_BOOL(in_nested, SpaprCpuState),
+        VMSTATE_INT64(nested_tb_offset, SpaprCpuState),
+        VMSTATE_STRUCT_POINTER_V(nested_host_state, SpaprCpuState, 1,
+                                 vmstate_nested_host_state, CPUPPCState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
 static const VMStateDescription vmstate_spapr_cpu_state = {
     .name = "spapr_cpu",
     .version_id = 1,
@@ -184,6 +259,7 @@ static const VMStateDescription vmstate_spapr_cpu_state = {
     },
     .subsections = (const VMStateDescription * []) {
         &vmstate_spapr_cpu_vpa,
+        &vmstate_spapr_cpu_nested,
         NULL
     }
 };
diff --git a/target/ppc/machine.c b/target/ppc/machine.c
index 7ee1984500..ae09b1bcfe 100644
--- a/target/ppc/machine.c
+++ b/target/ppc/machine.c
@@ -10,6 +10,7 @@
 #include "kvm_ppc.h"
 #include "power8-pmu.h"
 #include "hw/ppc/ppc.h"
+#include "hw/ppc/spapr_cpu_core.h"
 
 static void post_load_update_msr(CPUPPCState *env)
 {
@@ -679,6 +680,48 @@ static const VMStateDescription vmstate_tb_env = {
     }
 };
 
+static const VMStateDescription vmstate_hdecr = {
+    .name = "cpu/hdecr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(hdecr_next, ppc_tb_t),
+        VMSTATE_TIMER_PTR(hdecr_timer, ppc_tb_t),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static bool nested_needed(void *opaque)
+{
+    PowerPCCPU *cpu = opaque;
+    SpaprCpuState *spapr_cpu = spapr_cpu_state(cpu);
+
+    return spapr_cpu->in_nested;
+}
+
+static int nested_pre_load(void *opaque)
+{
+    PowerPCCPU *cpu = opaque;
+    CPUPPCState *env = &cpu->env;
+
+    cpu_ppc_hdecr_init(env);
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_nested = {
+    .name = "cpu/nested-guest",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = nested_needed,
+    .pre_load = nested_pre_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_STRUCT_POINTER_V(env.tb_env, PowerPCCPU, 1,
+                                 vmstate_hdecr, ppc_tb_t),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 const VMStateDescription vmstate_ppc_cpu = {
     .name = "cpu",
     .version_id = 5,
@@ -734,6 +777,7 @@ const VMStateDescription vmstate_ppc_cpu = {
         &vmstate_tlbemb,
         &vmstate_tlbmas,
         &vmstate_compat,
+        &vmstate_nested,
         NULL
     }
 };
-- 
2.34.1